1. Field of the Invention
The present invention relates to a liquid ejection head, a method of manufacturing a liquid ejection head, and an image forming apparatus, and more particularly, to wiring technology for electrical wires in a liquid ejection head.
2. Description of the Related Art
As an image forming apparatus, an inkjet printer (inkjet recording apparatus) has been commonly known, which includes an inkjet head (liquid ejection head) having a plurality of nozzles, and which records an image on a recording medium by ejecting ink (liquid) from the nozzles toward the recording medium while causing the inkjet head and the recording medium to move relatively to each other.
The inkjet head is, for example, principally constituted of: a common liquid chamber, which accumulates ink supplied from an ink tank; pressure chambers, which store ink supplied from this common liquid chamber; piezoelectric elements, which deform a diaphragm constituting one lateral wall defining the pressure chambers; and nozzles, which are connected to the pressure chambers. By supplying a prescribed drive signal to the piezoelectric element, the ink in the pressure chamber is pressurized and the ink is ejected from the nozzle in the form of a droplet.
In the inkjet head, various methods have been proposed for arranging the electrical wires and drive integrated circuit (IC) chips required to transmit drive signals to the piezoelectric elements, with a view to reducing the number of components, the manufacturing costs, and the size of the inkjet head.
For example, Japanese Patent Application Publication No. 2003-182076 discloses that IC chips forming drive circuits are fixed on a bonding substrate that covers the piezoelectric elements, the IC chips are mutually connected through wire bonding, and the IC chips and corresponding electrodes are also connected through wire bonding, so that the installation surface area of the IC chips can be reduced and the inkjet head can be made more compact. In this composition, however, since the connections between the IC chips and the connections between the IC chips and corresponding electrodes are made by wire bonding, then in an apparatus (e.g., a printer) that has moving mechanisms, there may be a possibility of disconnection due to vibrations or impacts, and therefore reliability is poor. Moreover, there are problems of workability and work efficiency in connecting the wire bonds, in view of the structure in which the electrodes to be connected with wire bonding are located on the bottom faces of recessed portions. Furthermore, since the structure is adopted in which the common liquid chamber is arranged on a lateral side of the pressure chamber, then the nozzle row and the common liquid chamber are required to be arranged alternately in order to arrange the nozzles in a matrix configuration for the purpose of increasing the nozzle density, resulting in the increased size of the head.
Japanese Patent Application Publication No. 2005-254616 discloses that a wall defining a common liquid chamber is partially formed of a flexible printed circuit (FPC) sheet, or the like, so that it is possible to reduce the overall size of the head of the inkjet printer. In this composition, however, similarly to the composition described in Japanese Patent Application Publication No. 2003-182076, since it is necessary to connect the wire bonds to the bottom faces of recessed portions in structural terms, then reliability may become poor and problems of work efficiency may also arise. Moreover, since the head is connected with external circuits through the flexible printed circuit having wires formed at high density, then the installation space of the head is accordingly increased.